Filling system for filling containers, such as bottles, with a liquid filling material using a normal pressure filling method are known. In such filling systems, before the start of the actual filling, a container being filled is pressed with its container opening sealed tightly against the filling element. Then, with the container still sealed against the filling element, a liquid valve is opened to begin the actual filling phase. During the filling phase, gas and/or vapor is expelled from the interior of the container as the filling material flows in. This gas is typically air or an inert gas resulting from a previous rinsing, such as CO2 gas. The expelled gas flows, via a return gas pipe that extends into the container, into a gas chamber of a tank that is common to all filling elements of the filling system. The tank is partly filled with the liquid filling material.
The flow of the liquid filling material into the container ends upon immersion of the lower end of the return gas pipe. The height of the return gas pipe thus determines the filling height of filling material in the container. This filling height is determined by an equilibrium between the geodetic filling material head, which is determined by the level of the filling material in the tank, and the filling material or liquid column formed in the return gas pipe and/or fluid channel internal to the filler element at the end of filling phase. The equilibrium point can therefore fluctuate. This can cause small fluctuations in fill level.
A known method of correcting these fluctuations is the Trinox method. In this method, the fluid channel internal to the filling element is pressurized with a pressurized gaseous and/or vaporized fluid. A suitable fluid is an inert gas under pressure, such as CO2 gas. In response, liquid filling material from the fluid channel internal to the filling element is returned out of a head space formed above the lower end of the filling pipe in the container, and out of the return gas pipe into the tank. After executing the Trinox method, the filling level in the container lies slightly below the lower end or lower opening of the return gas pipe. Typically, the fill level lies about 2 mm to 5 mm below the lower opening of the return gas pipe. This filling system is characterized by a simple and reliable construction.